One-pot preparation of poly[ 4-(5-oxy-1,3-dioxoisoindolin-2-yl) benzoyl] (PODB) crystals which was an aromatic poly(ester-imide) was examined by means of the reaction-induced crystallization during polymerization of 4-acetoxyphthalic anhydride (APA) and 4-aminobenzoic acid (AmBA). Two-step heating program was suitable for the formation of PODB crystals. The reaction of APA and AmBA at 150 degrees C, which was much lower than the polymerization temperature, was of importance to synthesize N-(4-carboxyphenyl)-4-acetoxyphthalimide. Even though the amide moiety was incorporated, the PODB crystals were formed as precipitates by heating at 150 degrees C and then at 280-350 degrees C. Morphology of PODB depended on the polymerization conditions and fibrillar crystals, rod-like crystals and ribbon-like crystals were obtained. This result provided a novel one-pot procedure for the control of the PODB morphology.